/*
   Copyright 2010 jcgarciam [at] gmail [dot] com

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

using System;
using System.Collections.Generic;
using System.Text;
using System.Data.OleDb;
using System.Data.Sql;
using System.Data;
using System.Data.SqlClient;
using System.Reflection;

namespace Cruddy.Persistence
{
    /// <summary>
    ///  A simple cache for IParametrizableEntity metadata during interaction with a given PersistenceManager.
    /// </summary>
    class MetadataCache : IDisposable
    {
        private Object _LOCK = new Object();
        private Dictionary<Type, WeakReference> cache = new Dictionary<Type, WeakReference>();
        private void SaveMetadata(Object parameter, FieldInfo[] metadata)
        {
            {
                if (!cache.ContainsKey(parameter.GetType()))
                {
                    WeakReference wref = new WeakReference(metadata);
                    cache.Add(parameter.GetType(), wref);
                }
            }
        }
        public FieldInfo[] GetMetadata(Object parameter)
        {
            lock (_LOCK)
            {
                Type key = parameter.GetType();
                if (cache.ContainsKey(key))
                {
                    WeakReference wref = cache[key];
                    if (wref != null && wref.Target != null)
                    {
                        return (FieldInfo[])wref.Target;
                    }
                }
                FieldInfo[] ret = GetFieldInfoMetadata(parameter);
                SaveMetadata(parameter, ret);
                return ret;
            }
        }

        private FieldInfo[] GetFieldInfoMetadata(Object parameter)
        {
            FieldInfo[] ret = parameter.GetType().GetFields(BindingFlags.Public |
                         BindingFlags.NonPublic |
                         BindingFlags.Instance);
            return ret;
        }
       
        #region IDisposable Members

        public void Dispose()
        {
            cache.Clear();
            cache = null;
        }

        #endregion
    }
}
